P0171 on a 2015 GMC Yukon

P0171 means the engine computer is adding more fuel than normal on bank 1 because it sees too much air or not enough fuel.

Not your vehicle? See general P0171 info.

Most common causes on the 2015 GMC Yukon

Ranked from 546 NHTSA owner complaints filed for this vehicle.

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1
Weak or leaking fuel pump, or a chafed/cracked fuel line causing low delivered fuel pressure
High severity
This platform shows a recurring pattern of fuel-delivery integrity problems - a fuel line rubbing through against the frame, a plastic fuel line worn through from chafing, a generic gas-line leak, and separate fuel-pump leaks/failures - any of which reduces fuel pressure/volume reaching the rail and can trigger a lean condition.
Reported in 5 NHTSA complaints
Parts:fuel pump fuel line
2
Clogged or failing fuel injector(s)
Medium severity
Owners had fuel injectors replaced after misfire/stumble complaints and a check-engine event; a partially clogged injector under-delivers fuel to its cylinder, contributing to a lean condition.
Reported in 2 NHTSA complaints
Parts:fuel injector
3
Vacuum or intake leak
Medium severity
A cracked hose or leaking intake manifold gasket admits unmetered air, causing the PCM to log a lean fuel-trim code.
Common cause
Parts:intake manifold gasket
4
Dirty or failing mass airflow (MAF) sensor
Medium severity
A contaminated or drifting MAF under-reports intake air volume, causing the PCM to under-fuel the engine.
Common cause
Parts:MAF sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open admits excess unmetered crankcase air into the intake, leaning the mixture especially at idle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the upstream oxygen sensor
Low severity
A leak ahead of the front O2 sensor draws in outside air, causing the sensor to report a falsely lean condition.
Common cause

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0171 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Rough idle
Hesitation
Surging idle
Poor fuel economy

What to check before replacing parts

Review short- and long-term fuel trims on bank 1

Look for: High positive trims (commonly worse at idle, improving with RPM) mean the computer is adding fuel to compensate for excess air or insufficient fuel — that pattern is this code's fingerprint.

Smoke-test the intake

Look for: Smoke escaping (or a hiss you can hear) at intake boots, gaskets, or vacuum hose connections confirms unmetered air is entering after the MAF sensor, which is the most common cause of a lean code.

Inspect the PCV hoses and valve

Look for: A cracked, split, or disconnected PCV hose, or a PCV valve stuck open, draws in extra unmetered air the same way a vacuum leak does.

Clean and test the MAF sensor

Look for: Visible dirt or oil film on the sensor element, or a grams/second reading that doesn't track expected airflow for RPM, means the MAF is under-reporting air and causing the computer to under-fuel.

Verify fuel pressure

Look for: Pressure below spec (weak pump, clogged filter, failing regulator) starves the engine of fuel and produces the same lean trim pattern as a vacuum leak — rule it out before chasing leaks.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough